This invention relates to a radio communication system comprises a switching office and a service area including therein stationary or fixed terminals and mobile terminals selectively communicating with the switching office through a plurality of radio channels, and in particular, to a channel assignment to a calling terminal in such a communication system.
In a known communication system of the type as described above, the switching office has a channel state memory having a table. The table comprises a channel number column having plurality of channel numbers, a channel state column representing using state of those channels, and a channel use column representing use of those channels. In more detail, in the channel state column, there is stored information whether those channels are currently idle or not, what terminal currently uses each of the channels and whether or not those channels are freely accessible by any one of terminals. The content in the column can be renewed. In the channel use column, there is previously stored that those channels are previously assigned to terminals, respectively. Usually, several, for example, three channels are previously assigned to three fixed terminals, while other channels are commonly and selectively used by mobile terminals.
The communication system has a control channel in addition to the radio channels for communication. The control channel is used for broadcasting the content in the channel state memory to all of the terminals. Therefore, the control channel is used for broadcasting assignment of one of common channels to a calling one of mobile terminals.
In the known communication system, since the fixed terminals are previously assigned with channels, it is impossible to freely increase the number of fixed terminals within the service area.
On the other hand, any one of the mobile terminals cannot use an idle one of the channels previously assigned to the fixed terminals. This is disadvantageous in the view point of the channel use efficiency.